


The curious case of the missing (____?)

by TheLittlestLlama



Series: Science dads timeline [1]
Category: Undertale (Video Game)
Genre: Angst, Depressed Sans, Don't blame me for my shitty smut writing, Fluff and Angst, Good W. D. Gaster, Implied/Referenced Self-Harm, Implied/Referenced Suicide, It's just backstory at the start, Kind of smut??, LMAO, Lmao my dudes grab a tissue, M/M, Mild Smut, Okay bye, Poor Sans, Sam if you read this one I'm going to fucking kill myself out of embarrassment, Sans Needs A Hug, Sans Remembers Resets, Sanster, Suicidal Thoughts, W. D. Gaster is not related to Skelebros, as it will connect to things later on, but I suggest you read it, kinda??, there is kind of smut after that tho lmao, well they were planning on doing it lmao
Language: English
Status: Completed
Published: 2017-06-07
Updated: 2017-06-07
Packaged: 2018-11-10 03:03:53
Rating: Mature
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 1
Words: 1,693
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/11118573
Author URL: https://archiveofourown.org/users/TheLittlestLlama/pseuds/TheLittlestLlama
Summary: Something is missing





	The curious case of the missing (____?)

**Author's Note:**

> Massive thank you to rag__tag for beta reading and putting up with me asking for help multiple times while I was working on this and for helping my confidence and telling me I should post it when I wasn't sure! She's such a sweetheart and I love her to bits. If you obsess over sanster like us, then go check out her fic called "Dr Gaster's assistant"! 
> 
> Also a slightly suggestive stuff warning lmao

Sans had lived through many resets.

 

A lot of genocides. 

Though he has forgiven Frisk, the physical and emotional scars are still there. 

Even if they're living on the surface. 

The many resets, including the many genocides, had really left their mark on Sans.

Literally and figuratively. 

The slash across his ribcage stayed with him throughout all the resets he painfully endured, and progressively got a little bit deeper with every reset-turned-genocide.

His depression grew along with the deepening of the scar, and so did the number of self inflicted scars he had on his body.

He didn't know exactly why he did it, but he was sure it served as a way to punish himself for doing fuck all to stop the human, and as a sort of tally to keep track of how many times the human reset. He wanted to see if he could still feel... 

 

Because all he felt was numb.

 

~~~~

 

"Hmm.. Hah, S-Sans... Mmm..." 

Gaster moaned, running his hands over the back of his partners ribcage. He was gripping the fabric of the hoodie his partner was wearing tightly in his hands as he sucked on his neck.

Sans slid his hands under Gaster's sweater, running his hands over the familiar flesh underneath, reaching for Gaster's sensitive spots, but steering clear of the cavity in the middle of his chest which held his soul.

"Nnnnnn..." Gaster moaned again, tilting his head back to give Sans better access when he found a sensitive spot on his neck.

Sans chuckled a little at Gaster's eagerness, loving how he was slowly coming undone even though almost no clothes had been thrown to the floor yet.

Sans pulled away from Gaster's neck, and he moved to hover his lips just an inch away from his. He moved forward and clicked his teeth against Gaster's lips gently, but after only a short moment, Gaster could feel his warm, wet tongue licking Gaster's lips in an ask to continue. Gaster eagerly opened up, and he quickly found himself being overtaken. Sans broke the kiss for a moment to tug Gaster's sweater over his head, and then was pushed back into the stack of pillows propping him up as Sans continued to explore his mouth.

Gaster put his hands on Sans's shoulders, and started sliding his jacket down. Sans helped him by shrugging it off his shoulders, and tossing it haphazardly onto the floor. 

Gaster broke the kiss and went to kiss Sans's collarbone, curling his tongue around it and making Sans let out a small hum of satisfaction.

Gaster started to lift the hem of Sans's shirt, and got about halfway, until he looked down and stopped what he was doing with his tongue to gasp.

 

Sans felt Gaster freeze, and was about to ask why he stopped, until he felt cold air hit his bare ribs.

 

His eye sockets went dark.

 

"o-oh shit..." 

 

"S-sans?" Gaster looked up at his blank expression frantically.

"W-what- what happened here? W-why is your rib... M-missing?" Gaster asked, starting to get worried. 

 

The front of Sans's third to last right rib was missing, it looked like it had been broken off. There were multiple little cracks in it that stemmed from where the main piece had gone, and it looked old, but painful.

Gaster knew that this wasn't a result of the big slash across Sans's ribcage which he had attained during the multiple genocide runs he had endured.

No, Sans had shown him the path of the scar before, and this rib was nowhere near the scar. 

Gaster was confused as to how something like this could've happened to Sans, and was about to ask why again, until he felt Sans shaking slightly.

"S-Sans?" He started tentatively,  
"A... Are you oka-" but he was cut off by Sans teleporting out of his arms.

"S-Sans?!" He called out, scrambling to get up.

He looked around the room hoping that Sans hadn't gone far, and he had to scan the room twice before he saw him. 

He was sitting with his knees drawn up to his chest in the far corner of the room. He was hyperventilating and his hands were surrounded by blue magic, and scrabbling to find purchase at his head.

All of the signs that he was having a panic attack.

He looked small... Small and scared and vulnerable. 

Gaster slowly stepped off of the bed, and crouched, so he was almost level with Sans. He started to crouch-walk slowly over to Sans, so as not to startle him so that he would teleport away again.

As Gaster got closer, he saw something moving out of the corner of his eye. He looked over to where he saw it move, and he saw a couple of items from around the room had been picked up and were suspended in the air with built up blue magic, just floating about.

'O-oh no...' Gaster thought.

He knew this could end up being harmful, to him or Sans, if it continued, so he needed to calm him down quickly.

As he moved a little closer, he could hear Sans hoarsely rambling something along the lines of "y-you weren't s-s-s-supposed to s-see I d-didn't want you t-to see you c-can't know ab-b-bout it," through his sobs and laboured breathing.

"S-Sans?" Gaster called out quietly. He took another half step forward towards his partner.  
"Darling? I-It's okay, I-I'm here, you're okay... I... I'm not mad if that's what you're th-thinking...." Gaster swallowed the lump in his throat.

"Just... P-please, you don't have to t-tell me anything at all... I-if you don't want to..." 

Sans made no change to show he was listening, still hyperventilating and scrabbling at his head.

"S-Sweetheart... Y-you need to breathe..."

Gaster reached out slowly, and touched Sans's forearm, resulting in Sans stopping his rambling, looking up sharply and jerking back his arm.

Gaster looked at Sans's tear stained face, nothing but pure fear in his eyes. He tentatively took his hand back, feeling extremely guilty that this was his fault.

Gaster thought back to the previous times they had sex, every time, Sans would insist keeping his shirt on, and now it seemed to make a lot more sense as to why.

Why hadn't Gaster remembered to not pull his shirt off this time? God, he was such an idiot...

"S... Sans? C-Can you hear me? Please say something..." He tried again, worry and concern evident in his voice.

".....y-you weren't meant to see it..." Sans whispered after a long pause to get his breathing under control. "You weren't m-meant to..."

"I-I know, and I'm s-so sorry..." Gaster said guiltily, tears beginning to prick in his eyes.

"Is..." He started, rubbing at his eyes "I-Is it okay if I hug you?" He asked tentatively.

A long moment passed, and Sans eventually nodded, allowing Gaster to move closer, and hug him to his chest.

Sans buried his face in Gaster's chest, sobbing yet again. A few tears of Gaster's own fell, and he hugged Sans to him all the more closer.

They sat like that for a bit, until Gaster thought that moving them both to the bed would be more comfortable.

"Sans? I-I'm gonna pick you up so you can sit on the bed, o-okay?" He asked gently.

Sans just nodded mutely.

Gaster carefully gathered up the small skeleton in his arms, then stood up slowly and lifted him bridal style, and walked over to the bed. 

He carefully lay Sans down on the bed and rearranged the pillows so it would be more comfortable, and then lay down next to him, putting an arm around him and bringing him closer, so they were facing the same way.

"Sans, I... I'm so sorry..." Gaster whispered. "I-"

"you didn't know..." Sans interrupted. 

"B-But I should've! I always thought that you insisting to keep your sh-shirt on when we're... You know, a little u-unusual... But I did it anyway... I'm so sorry..." 

"i-it's ok..."

They just cuddled in silence for a while, enjoying each other's company. Sans was feeling increasingly soothed by Gaster stroking his skull.

"Um... Sans?" Gaster started nervously, breaking the silence. "Uh... O-Only if you want to, c-could you maybe, ah, t-tell me what happened to your rib?"

Gaster could feel Sans tense up at the question, and stumbled over himself trying to back out of asking it.

"n-no..." He said softly, effectively stopping Gaster in his rambling, "i-it's okay... i can tell you if you want..."

"You don't have t-!"

"no... i don't want to hide from you anymore... so i guess you should know..." Sans said.

He rolled over on to his side so that he was facing his partner.

"w-well... you know how i've t-told you about the..." He paused and drew in a deep breath, "the resets... yeah?"

Gaster nodded, and Sans continued,  
"w-well... let's just say... that these," he lifts his forearm so Gaster can see, and points to the mass of self inflicted scars on his radius and ulna. 

"... got a bit out of hand..." He finishes softly.

"O-oh Sans... I'm so sorry...."

"it's fine... i honestly don't remember when i did it... it must have been about the thirtieth genocide..." He continued, 

"i couldn't feel anything... i just felt numb... i-i did it because i wanted to see if i could still feel... a-and also to punish myself... at one point i succeeded in..." He paused, drawing in a deep breath before continuing, 

"you know... actually going through with it... but i couldn't even do that right... as i would just come right on back..."

Gaster started to rub his back in hopes to comfort his small partner, as he could see the tears pricking in his eyes.

Sans sniffed and rubbed at his eyes with the heel of his hands. 

"b-but it's okay... it's over now. what happened, happened. what matters now is that i've learned from it, and i'm not like that anymore..."

Gaster hugged Sans even closer, and Sans did the same.

"... Thank you for telling me Sans." Gaster said softly, kissing Sans's skull.

"... love you 'dings..." Sans replied, before dozing off.

"I love you too."

**Author's Note:**

> Ahh! Thank you so much for reading! If you want more sanster, then maybe check out my other sanster fic, or check out rag__tag's longer sanster fic!


End file.
